Modify application.yml to change localhost to db

Containers in docker can be regarded as independent virtual machines. When mall-tiny-docker accesses localhost, mysql can not be accessed naturally. Docker containers can be accessed by specifying a good service name db. As for db, the name can be specified when running mall-tiny-docker container.

Packaging projects with IDEA and building mirrors

Note: Dependent basic images need to be downloaded first, otherwise there will be a build image timeout. For example, I do not have a Java 8 image locally, we need to pull down the image first, and then build with the maven plug-in.